The process of Shallow Trench Isolation (STI) is a standard process for forming isolation regions in a semiconductor substrate, which is widely used in semiconductor industry at present, especially in Ultra Large Scale Integration (ULSI) circuits. The process of STI includes three main steps of trench etching, oxide filling and oxide planarization. Compared to earlier isolation formation processes such as Local Oxidation of Silicon (LOCOS), the process of STI is more complicated.
It is already known in related art that a SOI (Silicon-on-Insulator) wafer is fabricated by the SIMOX technique. In this case, oxygen ions of a high dose are implanted into monocrystalline silicon to form an isolation layer under a high temperature condition, and then an annealing process is performed under a super-high temperature, so as to form a new type semiconductor material of a three-layer structure consisting of a top silicon layer, a buried silicon dioxide layer and a bulk silicon, see U.S. Pat. No. 6,740,565B2, titled “Process for fabrication of a SIMOX substrate”.
In view of the above, there is a need to develop a much easier isolation formation process by using techniques in the semiconductor micro fabrication field, such as SIMOX and/or other techniques to adapt to applications of the semiconductor industry.